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(No Model.)

J. F. SPRAGUE & F. J. KIPLING.

GLASS IMITATION SI-ONE FOR JEWELRY. Q

No. 261,402. Patented Ju1y18,1882

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UNITE STATES PATENT, OFFICE.

JAMES F. SPRAGUE AND FRANCIS J. KIPLING, OF PROVIDENCE, It. I.

GLASSVIMITATION STONE FOR JEWELRY.

SPECIFICATION forming part of Letters Patent No. 261,402, dated July 18, 1882. Applieation filed January 27, 1882. (No model.)

To all whom it may concern Be'it known that we, J AMES F. SPRAGUEand FRANCIS J. KIPLING, of Providence, in the State of Rhode Island, have invented an Improvement in Glass Imitation Stones for J ewelry, of which the following is a specification.

The nature of our invention consists in a cylindrically-bent glass imitation stone for jewelry, adapted to fit a metallic rim or setting by acid-etching at its fron t-surface edges; and our improvement is specially adapted to plates of glass imitation stone made in two superposed layers of different colors to imitate onyx, the satisfactory production of such imitation stone being impracticable by the ordinary process of glass-pinching as employed by lapidaries, and the grinding of the cylindrically-curved surface to fit the setting is too expensive.

Figure 1 represents a plan view of a plate of glass bent to a cylindrical surface. Fig. 2 represents an end view of the'same. Fig. 3 represents a plan viewof the imitation stone with its boundary-edges etched away, so that the remainin g front portion may fit the interior space ot'a metallic setting. Fig. 4 represents an end view of Fig. 3.

In the drawings, Figs. 1 and 2, A represents a plate of colored glass bent toa cylindrical surface. The boundary-edges of the rounded front portion of this plate are to be etched away, as shown in Figs. 3 and 4, so that the remaining front portion, a, Will be adapted to properly fit the interior space of a metallic rim or setting. The opposite edges 1) b of the cylindrically -hollowed back surface of the plate are ground thinner, in order that the plate may occupy less depth of space in the setting and rest squarely against the metallic back plate of the article of jewelry.

Curved glass plates for imitating stone in jewelry have heretofore been made from cylindrical tubes of glass out up into pieces of the proper size. for the purpose required; but such pieces are variable in their curvature and are not suitable for fine work.

We take flat strips of glass, and after heating bend them transversely over a mandrel or cylindrical form to the proper curvature with certainty and precision. We then divide the strips so prepared into suitable pieces and apply to the front of the glass plates a suitable stop ground of the exact size and form of the interior space of the setting-rim and place them in a bath of hydrofluoric acid, which cuts away the exposed front surface of the glass, as shown at a a in Fig. 4, the protected portion a being slightly undercut at the edges by the action of the acid, leaving a sharp corner at the front of the plate to fit the inner edges of the setting-rim, which may also be burnished into the undercut etched edge, thus securing the best quality of workmanship in the article produced.

The plate of glass A may be either made of a single color or of superposed layers of different'colors to imitate onyx.

We claim as our invention- The method of forming a glass imitation stone and adapting the same to fit the metallic rim or setting, which consists in first bending the glass plate to the form of a cylindrical segment and then acid etching the edges of the curved front surface, substantially as described.

JAMES F. SPRAGUE. FRANCIS J. KIPLING.

Witnesses:

IRA O. SEAMANS, SOGRATES SCHOLFIELD. 

